Conventionally, as refrigerant to be applied in a refrigeration cycle of an air-conditioning apparatus, an HFC refrigerant such as R410A, which is nonflammable and has a low ozone-layer depletion potential, has been used. However, R410A has a property of a high global warming potential (hereinafter referred to as GWP). Therefore, in recent years, in terms of prevention of global warming, it has been discussed whether the refrigerant to be applied should be changed to refrigerant having a low GWP.
In contrast, a slightly flammable HFC refrigerant such as an R32 refrigerant is present, which has a low ozone-layer depletion potential like R410A and has a GWP that is about one third of R410A. Furthermore, a highly flammable HC refrigerant such as R290 (propane), which is a natural refrigerant having a GWP that is about one seven-hundredth of R410A, has also been used. As is often the case, refrigerants having a low GWP are flammable, although they are different from each other in the degree of flammability.
In an air-conditioning apparatus using flammable refrigerant, in the case where an indoor air-sending device is in its stopped state when refrigerant leaks into an indoor space, a flammable concentration region may be generated. In general, such refrigerant is heavier than air, and the refrigerant which has leaked stays near an indoor floor. In view of this point, an air-conditioning apparatus has been proposed in which even when it is in its stopped state, if leakage of refrigerant is detected, the indoor air-sending device is operated to rarefy the refrigerant that has leaked, with indoor airflow (for example, Patent Literature 1).